American Medicine
April, 1907
Hypothesis Concerning Soul Substance Together with Experimental Evidence of The Existence of Such Substance

by Duncan MacDougall, M.D.
of Haverhill, Mass.

If personal continuity after the event of bodily death is a fact, if the psychic functions continue to exist as a separate individually or personality after the death of brain and body, then such personality can only exit as a space occupying body, unless the relations between space objective and space notions in our consciousness, established in our consciousness by heredity and experience, are entirely wiped out at death and a new set of relations between space and consciousness suddenly established in the continuing personality. This would be an unimaginable breach in the continuity of nature.

It is unthinkable that personality and consciousness continuing personal identity should exist, and have being, and yet not occupy space. It is impossible to represent in thought that which is not space-occupying, as having personality; for that would be equivalent to thinking that nothing had become or was something, that emptiness had personality, that space itself was more than space, all of which are contradictions and absurd.

Since therefore it is necessary to the continuance of conscious life and personal identity after death, that they must have for a basis that which is space-occupying, or substance, the question arises has this substance weight, is it ponderable?

The essential thing is that there must be a substance as the basis of continuing personal identity and consciousness, for without space-occupying substance, personality or a continuing conscious ego after bodily death is unthinkable.

According to the latest conception of science, substance, or space-occupying material, is divisible into that which is gravitative, solids, liquids, gases, all having weight, and the ether which is nongravitative. It seemed impossible to me that the soul substance could consist of the ether. If the conception is true that ether is continuous and not to be conceived of as existing or capable of existing in separate masses, we have here the most solid ground for believing that the soul substance we are seeking is not ether, because one of the very first attributes of personal identity is the quality of separateness. Nothing is more borne in upon consciousness, than that the ego is detached and separate from all things else - the nonego.

We are therefore driven back upon the assumption that the soul substance so necessary to the conception of continuing personal identity, after the death of this material body, must still be a form of gravitative matter, or perhaps a middle form of substance neither gravitative matter or ether, not capable of being weighed, and yet not identical with ether. Since however the substance considered in our hypothesis is linked organically with the body until death takes place, it appears to me more reasonable to think that it must be some form of gravitative matter, and therefore capable of being detected at death by weighing a human being in the act of death......

The net result of the experiments conducted on human beings, is that a loss of substance occurs at death not accounted for by known channels of loss. Is it the soul substance? It would seem to me to be so. According to our hypothesis such a substance is necessary to the assumption of continuing or persisting personality after bodily death, and here we have experimental demonstration that a substance capable of being weighed does leave the human body at death.

If this substance is a counterpart to the physical body, has the same bulk, occupies the same dimensions in space, then it is a very much lighter substance than the atmosphere surrounding our earth which weighs about one and one-fourth ounces per cubic foot. This would be a fact of great significance, as such a body would readily ascend in our atmosphere. The absence of a weighable mass leaving the body at death would of course be no argument against continuing personality, for a space-occupying body or substance might exist not capable of being weighed, such as the ether.

It has been suggested that the ether might be that substance, but with the modern conception of science that the ether is the primary form of all substance, that all other forms of matter are merely differentiations of the ether having varying densities, then it seems to me that soul substance which is in this life linked organically with the body, cannot be identical with the ether. Moreover, the ether is supposed to be nondiscontinuous, a continuous whole and not capable of existing in separate masses as ether, whereas the one prime requisite for a continuing personality or individuality is the quality of separateness, the ego as separate and distinct from all things else, the nonego.

To my mind therefore the soul substance cannot be the ether as ether; but if the theory that ether is the primary form of all substance is true, then the soul substance must necessarily be a differentiated form of it.

If it is definitely proved that there is in the human being a loss of substance at death not accounted for by known channels of loss, and that such loss of substance does not occur in the dog as my experiments would seem to show, then we have here a physiological difference between the human and the canine at least and probably between the human and all other forms of animal life.

I am aware that a large number of experiments would require to be made before the matter can be proved beyond any possibility of error, but if further and sufficient experimentation proves that there is a loss of substance occurring at death and not accounted for by known channels of loss, the establishment of such a truth cannot fail to be of the utmost importance.

One ounce of fact more or less will have more weight in demonstrating the truth of the reality of continued existences with the necessary basis of substance to rest upon, than all the hair-splitting theories of theologians and metaphysicians combined.

If other experiments prove that there is a loss of weight occurring at death, not accounted for by known channels of loss, we must either admit the theory that it is the hypothetical soul substance, or some other explanation of the phenomenon should be forthcoming. If proved true, the materialistic conception will have been fully met, and proof of the substantial basis for mind or spirit or soul continuing after the death of the body, insisted upon as necessary by the materialists, will have been furnished.